This disclosure relates to a data communications system for analog or digital signals, and in particular to systems using quadrature amplitude signal modulation. More particularly, the disclosure relates to the encoding of more than one information-containing signal source or channel with one source using a QAM modulation technique and the transmission of both encoded channels substantially simultaneously over the same communications link.
Although high throughput telecommunications networks do not constrain the size of the optical transceiver, optical transceivers for data center applications that use the Ethernet data communications protocol generally conform to IEEE 802.3 standard specifications and MSA form factors. Ethernet (the IEEE 802.3 standard) is the most popular data link network protocol. The Gigabit Ethernet Standard (IEEE 802.3) was released in 1998 and included both optical fiber and twisted pair cable implementations.
The 10 Gb/sec Ethernet standard (IEEE 802.3 ae) was released in 2002 with both optical fiber and twisted pair cabling. The 10 Gigabit Ethernet Standard specifications are set forth in the IEEE 802.3 ae supplement to the IEEE 802.3 Ethernet Standard are currently the highest data rate that has been standardized under the IEEE 802.3 framework. The supplement extends the IEEE 802.3 protocol and MAC specification therein to an operating speed of 10 Gb/s. Several Physical Coding Sublayers known as 100GBASE-X, 10GBASE-R and 10-GBASE-W are specified, as well as a 10 Gigabit Media Independent Interface (XGMII), a 10 Gigabit Attachment Unit Interface (XAUI) and a 10 Gigabit Sixteen-Bit Interface (XSBI) and management
Regardless of whether the system provides for one optical channel, or a WDM system with multiple optical channels, there is interest in increasing the information carrying capacity of an optical channel. Although various techniques such as PAM and QAM are known in the prior art, prior to the parent applications, it has not been known to utilize the jitter or inherent chirp associated with the transmitter to carry an additional information channel or bit.